1. Field of the Invention
This invention relates to a closure system including a closure having an integral tamper band connected to the skirt of the closure by bridges which fracture upon removal of the closure to provide a visual indication that the container has been opened or tampered with. More particularly, the invention relates to such a closure system in which axially extending ratchet members on the end of the tamper band and on the container cooperate to allow the tamper band to rotate with the closure as the closure is screwed onto the container, but prevent rotation of the tamper band as the closure is unscrewed to fracture the bridges joining the tamper band to the closure skirt.
2. Background Information
It is common practice today for container closures to have tamper indicating means which provide a visual and mechanical indication that the container has been opened or tampered with. Many of these tamper indicating closures include a tamper band secured to the skirt of the cap by frangible bridges which fracture when an attempt is made to remove the cap. When such tamper bands are applied to screw type closures, it is common to provide means to prevent rotation of the tamper band relative to the cap as the cap is unscrewed. Typically, this means has been radially extending ratchet members on the container neck and on the inner surface of the annular tamper band. Examples of such closures are found for example in U.S. Pat. Nos. 3,874,540 and 4,534,480. Such closures require very close tolerances on the closure and the container to assure proper engagement of the ratchets.
Many tamper bands are secured to the container by a radially inwardly directed lip which engages a radial flange or transfer bead on the container. Some of these tamper bands are provided with ratchet teeth which cooperate with corresponding members on the skirt to couple the tamper band to the cap during application of the closure to the container to resist premature fracturing of the bridges as the lip on the tamper band is forced over the transfer bead. When the cap is unscrewed, the inclined surfaces on the ratchet teeth cooperate to axially separate the tamper band from the skirt thereby applying an axial force to assist in fracturing the bridges. Closures with such features are disclosed, for example, in U.S. Pat. Nos. 4,461,391 and 4,560,076, and French patent no. 1,536,459. The closure in the second of these patents also utilizes radially extending ratchet teeth to prevent rotation of the tamper band as the cap is unscrewed. Such closures must also be made with close tolerances to preclude prying of the tamper band off of the transfer bead. Furthermore, the bridges must be made stronger to resist the twisting moment applied to them during application of the cap. This makes it more difficult to fracture the bridges on removal of the cap.
The closure disclosed in U.S. Pat. No. 4,503,986 has a tamper indicator made of a lower ring keyed to radial projections on the container to prevent rotation and joined to an upper ring of larger diameter by frangible bridges. Axially extending ratchet teeth on the upper ring cooperate with lugs on the cap skirt to permit relative rotation between the cap and the indicator as the cap is being screwed on, but lock the upper ring to the cap for rotation therewith during unscrewing of the cap to fracture the bridges. This closure requires both radial and axial engagement means for the tamper band and is more difficult and costly to manufacture. In addition, the tamper band is not integral with the cap, therefore requiring additional handling during application of the two piece closure to a container.
There remains a need for a reliable, inexpensive, easily manufactured closure with a tamper band which provides an indication that the closure has been opened or tampered with.
There is further need for such a closure which does not require tight tolerances either on the closure or the container to which the closure is applied.
There is also a need for such a closure in which bridges connecting the tamper band to the cap do not have to resist large forces during application of the cap so that they can be made to fracture with less force upon removal of the cap.
With regard to the need for such a closure which can be easily manufactured, the closure should be designed such that it can be integrally molded without the need for slides or other complex molding techniques.